Abstract [en]

In 1816 the Stirling engine was invented and has since been tested in a variety of applications. Cleanergy using Stirling technology in its solar and gas plants to produce electricity and heat. The goal of this work is to develop proposals for an energy-efficient way to control the cooling of a GasHub plant to the desired temperatures and draft proposals on combined heat and power solutions known as CHP (Combined Heat and Power). The method of work was to identify how the system looks like, customer visits and the development of proposals for improvement. A GasHub is a facility built out of a container in which this has been designed to connect and place GasBox units. A GasBox is a unit of the Stirling engine, generator and gas burners. A necessary feature of a Stirling engine is its cooling, partly to engine components is not too hot and partly to cool the heated gas. This is because the pressure and volume of gas to be reduced in the cooling phase of the motor to rotate. Cooling and heating system in GasHub linking together all GasBox where glycol mixed cooling water rotates around in a loop. The heat from the Stirling engines is transmitted in the heat exchanger to the cooled coolant from GasHub and in this way is reduced when the heat in the cooling system to Stirling engines. A GasBox produces about 7,2kW electricity when it runs on biogas and 20kW heat energy. The customers who have chosen to install the heating system uses this mainly to heat buildings and land heat outdoors to keep this clean of snow and ice. A GasHub 5 plant produces about 36 kW of electricity. According to the data Cleanergy has estimated the average parasitic loads to about 1.5kW or about 4% of the total energy production. A study was conducted on a GasHub facility in Ulricehamn to, among other things to find out how the customer experienced how large parasite loads were and what could be the reason for this. The calculations are carried out shows that the circulation pump is correctly sized. The pump needs to cope with a delivery height of 9 meters and need a flow of 8.6 m3 / hour. The result has three suggestions for improvement of control system for the cooling presented. The first proposal is control by the temperature, then the circulation pump speed is controlled so that a temperature difference of 12 degrees from the input heat to GasBox and out of this. The second proposal involves driving at various differential pressures for various operating conditions. The third proposal involves installing a thermostat on GasBox to regulate the heat out of it. The improvement proposal is about reducing waste heat and energy are proposed to isolate pipes in GasHub. Calculations show that it is possible to save 35kWh heat-energy per day. The proposals of the CHP solutions suggested that the heat can be used for air conditioning if an adsorptions-chiller is used. It is further proposed that the heat stored in the bedrock and cooling taken from there to cool GasHub. The discussion and analysis section of the report assesses improvement proposals and temperature differential regulation proposal is considered that it is relatively easy to implement and is the most optimal for the circulation flow and lower energy consumption. Among CHP proposals considered to be relatively easy to install an adsorptions-chiller to use the heat to the air. Furthermore, the chapter raises the question whether it would be possible to cool using a lower flow in the system because this could save more energy. The question of whether it would be possible to raise the temperature in the engine of a major gas coolers are used are highlighted. The conclusion of the report states that GasHub is today a fully functional facility for the production of electricity and heat, however, that there is much potential for improvement in the plant. It is found that rules the proposals is estimated to halve the energy consumption of the circulation pump.